The Integrated Office Viewer is not supported in Internet Explorer, both for on-premises Microsoft Office applications and for Microsoft Office 365. Since the OnBase Client uses Internet Explorer, the Integrated Office Viewer is not compatible with the OnBase Client.
For users who are still using Internet Explorer, it is recommended that you switch to a browser supported on the Web Client or use the latest version of the Unity Client. For information on which browsers are supported, see the Web Client browser requirements within the Installation Requirements documentation.